In the drilling of an oil well, the drilling lubricant is called drilling mud. It picks up cuttings from the bottom of the well and carries them to the top of the well and then to a mud pit where the chips or cuttings are separated. This permits the mud to be recycled and used again. The fluid flow system involving the mud is a high pressure system; accordingly, it is necessary to control this flow system with a choke. Chokes, however, run into great difficulties in that the mud and the cuttings carried by it are very abrasive. Because they are abrasive, they rapidly destroy the valve and seat mechanism in the choke.
The success or failure of the prior art devices is somewhat subjective dependent on the goals; nevertheless, the present apparatus meets a need and provides a solution for that need as is disclosed hereinafter. The improved relative wear factors and the related shutdown of equipment to replace the choke yields some evidence of the efficacy of the present apparatus and, in particular, point out how this device is able to control the highly abrasive volume of mud which flows through the mud handling system. It is very desirable maintain a regulated back pressure in the system; accordingly, control of this back pressure through the use of the present device and, in particular, the longevity of the device, signify the value thereof.